Current non-invasive (or minimally invasive) methods to assist outpatient clinical trials of therapeutics for Substance Use Disorders (SUD) are usually limited by issues such as 1) the inability to accurately and quantitatively monitor the frequency and level of a subject's illicit drug exposure and 2) uncertainty in assessing the level of a subject's adherence to the trial medication regiment. These limitations are mainly due to the technological challenges of (1) non-quantitative measurements, (2) inaccuracy, (3) requirement for frequent clinical visits, and (4) requirement for instrument and/or expertise for readout. Several available Point-of-Care (POC) ELISA platforms are able to screen drug usage qualitatively. However, the POC quantitative measurement remains an unmet, yet critical need in the assessment of drug abuse. Microfluidics has emerged as a potential approach for POC drug tests and personalized diagnostics, because of its potential capabilities for multiplexed and quantitative measurements, portability, low cost, high throughput, and other advantages. However, the full development of a platform that overcomes all the listed challenges has not yet been realized. Here, we propose a Multiplexed Volumetric Bar-Chart Chip (V-Chip) to assay for drug targets in diverse clinical samples, which integrates functions including quantitation, instrument free readout, portability, and affordability. Volumetric readouts, based on measurements of oxygen generated by a reaction between catalase and hydrogen peroxide, allow instant and visual quantitation of target drugs and biomarkers and generate visual bar charts without the need for external instruments, data processing, or graphic plotting. The development of the V-Chip thus marks a POC milestone and opens up the possibility of instrument-free personalized diagnosis and SUD management.